The Project explains, "GNOME 3.28 comes with more beautiful things! First, and most significantly, GNOME's default interface font (called Cantarell) has undergone a significant update. Character forms and spacing have been evolved, so that text is more readable and attractive. Several new weights have also been added -- light and extra bold -- which are being used to produce interfaces that are both modern and beautiful. Other beautiful things include GNOME's collection of background wallpapers, which has been updated to include a lovely set of photographs, and the selection of profile pictures, which has been completely updated with attractive new images to pick from."
Unfortunately, you can't just click on a button and upgrade to GNOME 3.28 today. Actually, for the most part, you will need to wait for it to become available for your operating system. Sadly, this can take a while. Fedora users, for instance, will have to wait for a major OS upgrade for it to become available.